These are the single most important piece of equipment when it comes to birding. Binoculars are typically described by two numbers (e.g. 7X35, 10X50). The first number indicates the magnification power; the second number is the diameter in millimetres of the front-facing lens (known as the objective lens). You may think the higher the power, the better, but there is a trade-off. Anyone with experience in photography can tell you that higher magnification means a narrower field of view and a darker image and the same applies to binoculars.
A wide field of view and tons of light are crucial to effective birding. More light provides a brighter, sharper image and allows you to see more contrast in adverse light conditions. A wide field of view, aside from enhancing light-gathering capacity, makes it much easier to pick out birds at a distance or small birds moving in the undergrowth or canopy. Also, the higher the magnification, the harder it is to hold the image steady by hand. This makes anything higher than 10X impractical for birding.
With regard to field of view and light, there are two factors that influence this. The first is the diameter of the objective lens, and the second is the angle of the lens. Let’s look at these factors in turn.
The larger the objective lens, the more light it allows to enter the binocular. Once again though, there is a trade-off. The larger the objective lens, the larger and heavier the binoculars. Even a relatively small pair of binoculars can feel like a cinder block around your neck after eight straight hours of birding. Different styles of binocular construction, though, can alter this relationship between objective lens, size and weight.
All binoculars currently available fall into one of three design categories. The traditional design, where the objective lens is offset from the eyepiece is known as “porro prism” (Fig. #1). The design that has the objective lens directly in line with the eyepiece is known as “roof prism” (Fig. #3). The main advantage of the roof prism style is that it allows for a much more compact size and a marginally lighter weight than a comparable porro prism binocular would have. This has made roof prism binoculars very popular among the birding set. Roof prism binoculars, however, do require an extra set of prisms and this makes them relatively more expensive to manufacture. One idea manufacturers came up with to retain the less expensive porro prism design yet cut down on size was to offset the objective lens to the inside of the eyepieces instead of to the outside. This third design type is referred to as “reverse porro prism” (Fig. #2) or sometimes “inverted porro prism”. None of the design types has any inherent advantage over the others when it comes to the quality of the image .’ it’s strictly a size, weight and aesthetics thing.
With so many possible combinations of magnification power and objective lens size, is there a way to compare the light-gathering capacity of binoculars with different characteristics? Well, I’m glad you asked that question (you were thinking that weren’t you?). The answer is yes. The way to bring any power/objective lens combo down to a common denominator is to calculate something called “exit pupil”.
Exit pupil is the diameter, in millimetres, of the shaft of light that enters the eye. The larger this number, the more light is reaching the eye. Exit pupil is calculated by dividing the objective lens by the magnification power. A 7X35 binocular would have an exit pupil of 5(35/7=5). If you wanted to go up to a 10 power binocular, but didn’t want to sacrifice light, you would need a 50mm objective lens for it to be comparable. If it was an 8 power binocular you would need a 40mm objective lens. In terms of light-gathering capacity the supreme combo that is regularly available is the 7X50 (with a huge 7.1 exit pupil), but these tend to be big and heavy.
The field of view can be described in two ways. It can be described as the width in feet (or meters) across the field of view at one thousand yards (or one thousand meters) or, more commonly, as the angle of the field of view expressed in degrees (see figure # 4) .
The angle of the average pair of binoculars is usually less than 8 degrees, but some binoculars are designed to provide a wider than usual field of view. These types, known as “wide angle” binoculars, tend to be uncommon in the stores, but they are worth hunting for. Wide angle optics allow more light to enter the eye, and also make it a lot easier to pick up on moving objects … perfect for birding! There is no strict definition of “wide angle”, but any pair with an angle of 8 degrees or higher could be considered such. 11 degrees is the maximum I have seen for a 7X or higher power binocular.
The aging of the baby boom population is probably the primary reason why interest in such leisure pursuits as golf, gardening and birdwatching has exploded over the last fifteen years or so. A basic law of business is that capital gravitates to growing markets, and we can see this phenomenon at work in the birding world. In the last few years, there has been a dramatic proliferation of brands and models of binoculars available for sale to birders. Like anything in life, this situation has both good and bad in it. The good is that there is more selection and lower prices. The bad is that too much choice often leads to difficulty in making a decision, not to mention confusion and conflicting ideas and opinions over what is best. In a crowded market, it is often the manufacturer with the most aggressive marketing that sells more product. Thus, I have seen many types of binoculars marketed as being specifically designed for birding, that don’t have what I consider to be the best characteristics. So what are the optimum characteristics for the perfect birding binocular ? Well … if you talk to ten birders you may get several different answers. Some feel field of view is most important, others feel magnification power is paramount, others opt for small size and weight. It comes down to personal preferences but here is a few guidelines based on my own experience.
Magnification power should be a minimum of 7X and a maximum of 10X. This guideline will, in effect, leave you with three choices: 7X, 8X or 10X, because these seem to be the standard for manufacturers. 9X is not unheard of but seems to be uncommon. 8X is a good all around power. It is slightly higher than the 7X and yet is generally a lot smaller and lighter than a 10X with, typically, a much better field of view. Ideally, the exit pupil should be about 5.0 or higher, but I would recommend an absolute minimum of 4.0. Angle of the field of view should be at least 8 degrees or higher, although if you opt for a 10X power you may have to settle for something less. The higher the power, the harder it is to incorporate a wide angle of view. Keeping this design limitation in mind, I would only settle for an angle of less than 8 degrees if it is a 10X. If you opt for a 7X or 8X, you should be able to find 8 degrees or higher.
Thus, in my opinion, the best overall combination of magnification, field of view, light-gathering capacity, size and weight is 8X40 wide angle roof prism binoculars.
Ultra compact “opera glass” style binoculars are somewhat popular because of their tiny size and weight. Part of the size reduction is achieved through their roof prism design, but a lot of it comes from a narrow objective lens. The field of view on most of these is so narrow that you get the impression you’re looking through a pipe and this makes them mediocre for birding. I think the last pair of this type I tried were 8X21. Well, a miniscule 2.6 exit pupil is fine if you’re contemplating the ponderous bulk of an opera singer on stage, or perhaps watching your favourite heavy metal rocker pounding his head into the drywall, but try to catch a fast moving warbler at thirty yards. By the time you figure out you’re looking at the right twig, the bird is in the next county! This is why a large exit pupil and a wide angle of view is so important. It’s much more forgiving if you’re trying to nail down a moving bird or trying to distinguish a tiny bird in a mass of foliage.
Often you will hear the expression “eye relief” in reference to binoculars. If you hold your eyes right up to binocular eyepieces, you will see a round image. Slowly moving the binoculars away from your eyes, you will notice that the size of the image doesn’t change for the first few millimeters, but beyond a certain point the image in the eyepiece starts to shrink. The point immediately before the image starts to shrink is known as the “eye relief” of the binocular. By definition it is the maximum distance, in millimeters, between the eyepiece lens and the eye that will still allow the user to see the full image right up to the periphery of the field of view. The eye relief number is only really useful as a comparison between different binocular models. It is described in terms of length and generally the larger the number (meaning a “longer” eye relief) the better. Binoculars with a long eye relief are easier to use and cause less eyestrain when used for extended viewing. As well, if the viewer will be wearing eyeglasses when using the binoculars, a long eye relief is essential because the eye can’t get that close to the eyepiece lens.
Another term you will sometimes hear in reference to optics is “coated”. When light passes through glass, which is what an optical lens is made of, some of the light rays get scattered. It was discovered that covering the surface of a lens with a micro-thin film of magnesium fluoride reduces this scattering effect dramatically so that more light reaches the eye. As well, the film has the effect of reducing glare so the overall image is clearer. The expression “coated” usually means only the external surface of the lens is covered with this film. If both external and internal surfaces of the lens are covered, it is referred to as “fully coated”. Sometimes manufacturers put several layers of this film on the lens and this is referred to as “multi-coated”. You want to make sure any binoculars you purchase are “fully coated” or “fully multi-coated”, but this shouldn’t be a problem as it is pretty much standard these days on all grades of binoculars. It is hard to find a pair that is not fully coated.
Many binoculars come with a thin rubber or polymer coating on the barrels known as “armour”. Armouring was originally intended primarily to provide a shock-absorbing layer of protection and enhanced water resistance for rough handling uses such as hunting or military. Most manufacturers now incorporate this feature into their optics for comfort of grip and aesthetic reasons. From a birder’s viewpoint, the biggest benefit of armouring becomes apparent in cold or windy weather birding. Even with gloves on, holding on to a piece of metal all day can suck the heat from your fingers. Your hands will stay somewhat warmer if that piece of metal is covered with rubber.
Some binocular models are waterproof and, even if you don’t drop them off the dock into ten feet of water, it is still a handy design feature to have. This is because if you are birding in inclement weather, particularly heavy rain (hey…the birds don’t mind it…why should you?), water vapour can sometimes seep inside the barrels of the binoculars. If it subsequently condenses on the inside of the lenses and prisms (which it often does) you are through birding for the day. The real tragedy of this situation is that you will then be deprived of the unique and singular pleasure of being outside through many long hours of cold, drenching rain as you wander who-knows-where in search of gosh-knows-what. If your binoculars are waterproof you are far less likely to miss out on the fun! Keep in mind, though, that binoculars that are watertight tend to be quite a bit more expensive than comparable models that are not.
There are lots of stores, such as camera or nature shops that carry binoculars. Two of the better stores I have visited in the Lower Mainland when it comes to selection are:
A&A Astronomical, a Division of
Harrison Scientific Instruments
1859 West 4th Avenue
V6J 1M4 Canada
Tel: (604) 737-4303
Vancouver Telescope Centre
2220 West Broadway
V6K 3E3 Canada
Tel: (604) 738-5717
When it comes to selection and price, it’s tough to beat the internet, but the big drawback to ordering it through the net is that you don’t get to see the real thing and touch it …. feel it …. try it out before you own it. No matter how good a thing may look, how good the description may sound, or how glowing the testimonials in the online catalogue, you just never know exactly what you’re getting, or if it’s suitable for your particular preferences, until you have the actual item in your hot little grasp. You either have to be prepared to take that gamble, or else familiarize yourself with certain models at local retailers, and then use the internet to hunt down the best price. Many of the sites listed in the “internet” section, have online stores. Probably one of the best of these is the site operated by American Birding Association Sales Inc.
ABA Sales is a mail-order company that was established solely for the benefit of the American Birding Association, one of the largest bird study organizations in the world. You do not, however, have to be a member of the ABA to shop there. Because it is a site operated by birders for birders, the selection and prices are great.
Four other very good websites for birding optics are Pelee Wings, Binoculars.com, Eagle Optics and Efston Science.
B.C. Telescopes and Nature has a great online store that offers a wide selection of telescopes, binoculars and accessories from the major manufacturers and they ship anywhere in Canada. You can visit the store at www.bctelescopes.com or call them at 250-245-9356 or toll-free at 1-866-245-9356.
If you consider the size of the investment, the fact that you will be using it for years to come, and that the right pair of binoculars will greatly enhance your birding enjoyment, it is definitely worth it to shop around and compare (okay, okay ‘ I know I sound like your mother, but it’s true). Prices for similar models can vary quite dramatically and sometimes quality can vary quite a bit at the same price range. Occasionally, stores will be trying to clear discontinued models, and in this situation you can sometimes get excellent deals.
Generally, American (eg: Bushnell, Bausche & Lomb, Celestron) and Japanese (Nikon, Pentax, Kowa) models tend to be less expensive and German (Zeiss, Leica) or Austrian (Swarovski) made binoculars more expensive. Although there is a perception about quality being commensurate with price (we’ve all heard that old aphorism, “you get what you pay for”) there are many fine models with great optics available in the $200 to $500 range that will last you for ages. If, on the other hand, you feel you simply must have that pair of Swarovski 10 X 42 ELs, then take comfort in the fact that, although your pocketbook will be $2,000 lighter, at least you will be the envy of some members of the local birding community.
Here’s a tip to gauge the quality of the optics of any pair of binoculars you are considering. When you look through binoculars, the image you see is basically round. Pay special attention to the edges of the round image. Binocular lenses are convex and this shape causes distortion of the image as you get closer to the edge of the field of view. There are ways the lens can be ground to eliminate this distortion, but as you might guess, it takes a lot more craftsmanship to do this. The entire image on good quality optics should appear flat and the edges should be as sharp and clear as the centre. If the edges appear out of focus, or fuzzy, or give the slight impression of the convexity of the lens (the “fish eye” effect), then the quality of the binoculars is not that good.
Adjusting your binoculars for your eyes
To provide a proper, clear image, it’s important that your binoculars be adjusted for your eyesight. To do this, follow these simple steps:
The piece connecting the two barrels, (also known as the prism tubes), of the binoculars is hinged allowing the barrels to be moved closer together or farther apart. This is how you adjust them for the width of your eyes and this is the first step.
All binoculars allow one eyepiece to be adjusted independently of the rest of the binoculars (it is usually the right eye-piece). This eyepiece is known as the “diopter” and its purpose is to compensate for the fact that many people have different eyesight in each eye.
Close your diopter side eye, and, using the binoculars centre-focusing wheel, focus on some object looking only through the non-diopter side of the binoculars.
Once you have done this, switch the eyes. Close the non-diopter side and look only through the diopter side. Focus on the same object by turning the diopter until it appears clear.
Then open both eyes. The binoculars should now be adjusted for your eyes.
Use the centre-focussing wheel to focus as necessary, but you should not have to touch the diopter again.
Note the diopter setting though, because it can get moved from that setting through handling, storage, lending to friends, whatever.
The type of telescope used by birders and hunters is known as a “spotting” scope. This expression is used to distinguish the type from a typical astronomical telescope. For the experienced birder a good spotting telescope is indispensable. It is very useful in situations where you can’t get close enough to get a good image in your binoculars. Examples would be birds sitting on a distant tree, waterfowl a fair distance from shore, or a flock of shorebirds on a mudflat. Because of the high power involved, a telescope must be used with a tripod. This kind of setup may seem cumbersome for birding, but it’s just a question of experience in handling. You would be surprised how fast an experienced birder can set up a scope and zero in on a distant bird.
Spotting scopes generally come in two objective lens sizes … 60mm and 80mm. As with binoculars, the larger objective lens will give you a much wider field of view and more light, but it also means a larger and heavier scope. I have found 60mm to be more than adequate for most birding applications. Magnification power should be around 25 to 30X. Many scopes come with a zoom eyepiece, which is useful, but make sure the low end can come down to 25 or even 20 power. Most often this magnification will suffice. Once again, just like binoculars, the higher the magnification power, the harder it is to use. This is especially true with telescopes because the field of view is extremely narrow compared to binoculars (an exit pupil of between 2.0 and 3.0 is normal for spotting scopes).
As with any other sport, when you progress to a more advanced level the costs go up. Expect to spend at least $500+ on a decent scope (much more for a higher quality model), and you can add to this $100 to $200 for a low-end tripod. Tripods tend to take a lot of abuse during birding forays so it may be better to spend a little more for a sturdier model. At the same time, however, it must be relatively compact and lightweight so you can cart it around comfortably. It’s a question of finding the right balance of size, weight, ruggedness and ease of use. Adding a scope and tripod to your birding arsenal may seem expensive but my own experience has been that the increase in birding capabilities and enjoyment brought about by owning a scope has utterly dwarfed the cost involved. Besides, my first scope, which wasn’t an expensive model, has only required one minor servicing (strangely enough right after the warranty expired) in 26 years of use.
A zoom lens that will allow you to change magnification power without switching eyepieces, is a very convenient feature to have for birding. One thing to keep in mind, though, is that a zoom lens is a moving part and more moving parts means more things that can go wrong. It’s just something to consider, especially if you tend to be rough on your equipment. I would recommend that if you opt for a zoom lens, it’s better to spend a little more for quality.
All of the binocular retailers mentioned earlier in this section will have a selection of spotting scopes.
For those of you with internet access who would like to see a more detailed discussion and analysis of birding optics I would highly recommend visiting the following sites:
- Optics for Birding
- Better View Desired
- Cornell Laboratory of Ornithology’s binocular evaluation
- Opticsfinder.com (if you are in the market for a pair of binoculars, this latter site is useful because it has a search facility that allows you to enter a number of parameters, such as anticipated uses and amount you would like to spend, and it will list the models that match your guidelines)